1. Field of the Invention
The present invention generally relates to disc cartridges and, more particularly, is directed to a disc cartridge which can be recorded and/or reproduced while accommodating therein a disc-shaped record medium such as a magneto-optical disc or the like.
2. Description of the Prior Art
Japanese Utility Model Application Nos. 1-22572 and 1-63698 describe disc cartridges in which an optical disc is rotatably accommodated and in which a signal can be written in and/or reproduced from the optical disc accommodated by an optical pickup head device.
In these previously-proposed disc cartridges, an opening portion is provided to expose one portion of the accommodated optical disc in order to write and/or read out (i.e., record and/or reproduce) a signal therein and/or therefrom by the optical pickup head device. Also, a shutter is provided to close the above-mentioned opening portion so that foreign substances, dusts or the like can be prevented from entering the disc cartridge or that the surface of the optical disc can be protected from being touched with fingers, hands or the like.
The shutter is provided with a guide member and the guide member is engaged with a guide groove formed on a cartridge body, whereby the shutter can be slidably moved in the direction of the opening portion along the guide groove. Further, the shutter is spring-biased by a force of a spring member so that it always closes the opening portion. Thus, when the disc cartridge is not in use, the opening portion is held in its closed state. When the disc cartridge is loaded on a recording and/or reproducing apparatus, the shutter is opened by a shutter releasing mechanism of the recording and/or reproducing apparatus against the spring-biasing force of the spring member, whereby the opening portion is opened thereby to allow the accommodated optical disc to be exposed to the outside.
In the thus constructed disc cartridge, the shutter slidably attached thereto to open and/or close the opening portion of the cartridge body is formed by punching and bending a metal thin plate such as a stainless steel plate or the like in accordance with a configuration of the opening portion or the like.
When the shutter is formed, its closing surface portion corresponding to the opening portion, the guide member and the engaging member engaged with the spring member are also formed simultaneously. In that case, the guide member is formed by bending a narrow plate member whose width is considerably small as compared with the closing surface portion so that the guide member has such a configuration that is very weak for an external force. Thus, the guide member is easily deformed to the outside, or the guide member tends to stretch regardless of the bending-process. There is then the substantial disadvantage that the guide member will be disengaged from the guide groove formed on the cartridge body, thus urging the shutter to be disengaged from the cartridge body unintentionally.
In the disc cartridge in which the shutter is provided with only one guide member, the shutter is easily shaked when it is slidably moved relative to the cartridge body to open and/or close the opening portion so that the shutter cannot be opened and/or closed smoothly.
Further, in the previously-proposed disc cartridge described in Japanese Utility Model Application No. 1-63698, the shutter is provided with a pair of guide members so that the shutter can be smoothly slid relative to the cartridge body. In that case, however, the two guide members of the shutter are inserted into and engaged with guide grooves formed on the major surface of the cartridge body and these guide grooves are formed along the front edge of the major surface of one part (or half) of the cartridge body. For this reason, the thickness of the major surface at its portion where the guide grooves are formed is reduced considerably so that a mechanical strength of the cartridge body is decreased. Particularly, when this type of disc cartridge is loaded on a recording and/or reproducing apparatus, there is the substantial risk that the disc cartridge will be damaged by a shock applied thereto through the shutter.
Furthermore, the configuration of the shutter itself is very complicated and needs a cumbersome manufacturing-process, which unavoidably increases a manufacturing cost of the disc cartridge.